Process of separating meta and para cresol.



UNITED STATES PATENT QFFICE.

FRITZ RASCHIG, OF LUDWIGSHAFEN, GERMANY.

PROCESS OF 'SEPARATING META AND PARA oR'EsoL.

SPECIFICATION forming part of Letters was No. 655,117, dated July 31, 1900.

Application filed October 4:, 1899. Sarielll'o. 732,562- (No specimens.)

To all whom it may concern:

Be it known that I, FRITZ RASCHIG, a subject of the King of Bavt'iria, residing'at Ludwigshafen=on-the-Rhine, Germany, have invented certain new and useful Improvements in Processes of Separating Meta-Gresol and Para-Oresol, of which the following is a specification.

As is Well known, coal-tar and the phenol mixture obtained therefrom contains all the three isomeric cresolsnamely, ortho, meta, Now, inasmuch as it is in and para cresol. inost cases only its disinfecting property which determines the employment of cresol for technical purposes, and this property being equally possessed by all three isomers alike, the mixture was generally used without any attempt being made to separate it into its components. the increased useof cresol for the preparation of chemical compounds for other purposes and the necessity for obtaining these products in a pure state a separation of the cresols from each other in a pure condition suggested itself. Thus trinitro-cresol, which is obtained by first sulfonating the cresol mixture and subsequently treating it with nitric acid in a manner analogous to the prepara-.

tion of picric acid from phenol, has been used as a substitute for picric acid for some time. This trinitro-cresol is a derivative of metacresol, the Whole of the ortho and para cresol originally present in the cresol mixture becoming oxidized and completely disappearing in the process of nitration. It is obvious that this oxidation requires large quantities of nitric acid, and since the mixture of the three cresols from coal-tar is generally composed of thirty-five per cent. meta-cresol, twentyfive per cent. para-cresol, and forty per cent. ortho-cresol it will be seen that it requires three times the quantity of nitric acid to nitrate this mixture which would be necessary for convertingonly its percentage of metacresol into trinitro-meta-cresol.

In order to out down the amount of nitric acid used, the isolation of the pure meta-cresol from the cresol mixture suggested itself. It is possible to eifect the separation of the ortho-cresol, which distills at 188 centigrade, from meta and para cresol distilling at 200 centigrade by fractional distillation, thus ob- In view, however, of

taining a cresol mixture which consists of about sixty per cent. meta-cresol and forty per cent. para-cresol and the nitration of which will only require double the quantity of nitric acid corresponding to the sixty per cent. of meta-cresol present; but a process to separate the para-cresol from the meta-cresol has not been found heretofore.

By my invention, which is based upon the ready solubility of meta-cresol-sulfonic acid in sulfuric acid and the very great difficulty experienced in dissolving therein both paracresol-sulfonic acid and its sodium salt, all these inconveniences are avoided and an easy separation of the para-cresol efiected.

In carrying out my invention the commercial mixture of meta-cresol and para-cresol is heated with an amount of concentrated sulfuric acid or to ming sulfuric acid in excess of that required for the conversion of the cresols present into their respective sulfoacids until the formation of these sulfo-acids is completed. The resulting product is then allowed to stand until the para-cresol-sulfonic acid has crystallized out, whereupon the crystals are removed from the mother-liquor. The crystals of the para-cresol sulfonic acid are precipitated with special rapidity when after the sulfonation a small quantity of wa ter is added to the product of the reaction. The precipitate is hydrate of para-cresoLsulfonic acid, which crystallizes in large crystals which can be readily separated by filtration from the solution.-

The sodium salt of thepara-cresol-sulfonic acid being, as already stated, insoluble in sul furic acid, the para-cresol-sulfonic acid obtained in the manner described may beconverted into its sodium salt by an addition of sodium sulfate or of other readily-soluble sodium salts, such as acetate and carbonate or chlorid of sodium, the sodium salt of the para-acid being likewise easily separated by crystallization. group by means of superheated steam in the usual manner the cresols can be obtained in a pure state from their sulfo-acids.

Example 1: For instance, for carrying the said invention into efiect I may use about twenty pounds of a technical mixture of about sixty per cent. meta-cresol and forty per cent. para-cresol, which is dissolved in By splitting 01f the sulfo the mother-liquor in this casebeing subjected eighty pounds of concentrated sulfuric acid,:

the resulting solution being heated to 1 00 centigrade for-one 'hour. It is then allowed to stand for abouta Week at an ordinary temperature, during which time a pasty mass of crystals will be formed, which are crystals of para-cresol-sulfonic,acid, andfthe' mother-TI liquor remaining consists of meta-cresol-sulfonic acid and an excess ofsnlf uric acid. n The crystals may be separated from the liquor by filtration or by means of presses or centrifu-n gal machines; From. thecrystals, as well as from the liquid, the combined sulfuric acid may be split off by superheated steam and" pure para-cresol and meta-cresol obtained;

In case, however, it is desired to obtain trinit-rmmeta cresol this step is not necessary,

to, direct nitration. The. great industrial im-v provement efieoted by this mode of operation will be apparent from the following figures: Twenty pounds of the above-named mixture of meta -'cresol and para-cresol require for their perfect. nitration two hundred pounds of nitric acid of 1.38 specific gravity (40 Bauml'and yield twenty pounds trinitro metac'resol. If, however, the para-cresolhas, been first separated out in the form of its sulfa-acid, there will be required only one hundred pounds of nitric acid to eifec-t a complete. nitration, with a yield of nineteen pounds of trinitro-meta-cresolr The slightly; 1

lower yield; is duetoa small part ofthe metai cresolesulfonic acid adhering to the crystals; of the para-acid, and thereby escaping nitra tion; but the cost of that one pound less in yield 0 f the nitro product doesnot amount toone-tenth-of the. economy elfectedby the j one hundred pounds of nitric-acid saved,

ExampleZ: Ten kilograms of a mixture-of meta. and, para cresol are dissolved in thirty kilograms of f umjng sulfuricacid containing; twenty per cent.- of S0 The temperature is therebyiraised. up. to 160 centigrade and the sulfonation takes place quickly and with out any heating. The solution is then cooled and mixed under continuous cooling with ten liters of water, so that, the temperature does not exceed centigrade.

solidifies completely withintwenty-four hours and is. then treated in, the same manner as in Example 1.,

Example 3: Twenty pounds of 'the same mixture'of meta-cresol and para-cresol, as in Example 1, are dissolved in fifty pounds concentrated sulfuric acid and heated ..to'100 centigrade for one hour. A warm solution of eight pounds anhydrous sodium sulfate in forty pounds water is then added, and after being thoroughly mixed the whole is set aside until perfectly cool. "The-resultant paste of crystalsconsists ofcrystals of the sodium salt of the.para-cresol-sulfonic acid, and the other-liquor consists of meta-eresol-sulfonic acid and sulfuric acid "with small quantities (of the sodiumsulfa'teiadded in excess. The crystals and liquor are then separated, and the latter may be either subjected to directni a i n, or aybe-chang into meta-cresol y h io o st ams hough I pr e t use the severalingrediw i the Pr port ons enumerated in the ous that these may be varied to some extent without deviating from the; spirit of myin; n i n as to suit existing conditions- Thus the, amou t o sulf ri acid used inthe rst xample may b ecrease espec al y' n. the, winter, en i is possib e to 1. the souti n bel the ordina y temperature.

Having th s.- eri e my invention, I claim a ew and desi e iecure by Letters.

Pa en e sep ration of; metasol: nd. para-cresol, ich c sists-in; fi st; nve ting the ni nto 1 su-l oracids a d su eq ently sepa ating the ;,soiid pa aracid from he iquid me a-acid. s sta' ti Hy a s for ha a 2., The hereinribe p oce s forthe s pa a i n, of me acres l a d para-cresol, h h QO SistS infirs-t c nzve z gt mints their esp c ve snlfo-acids-Sen re T e: the S di pa m cid om. the iquidmeth-add and. ifipally t ating ea h: suite-m d; with steam for eco e ng he. cr so .herefrmn', substantially asset forth. n ti y tha c aim the feresein g; my i e i I ha s -gnedmy a e n presence of two subscribing; wizt nessesz-n f FRITZ RASQIFHGL Witnesses:- V

FR. Josnn DoRFEL,

LUDWIG BURKA n,

The he e n escribe p esses for the above; ns ances ofropera ion, sti l itis; ObVir' 

